These days it is important how to recycle or reuse the plastic materials which have been sold and used-up once and finished their lives in order to protect environment, to save total energy and maybe reduce the cost. On the market are a variety of Film with Lens Units (e.g., a so-called Single-Use camera) with simple photographing mechanism and preloaded photographic film. Most of components of the Film with Lens Units are made of plastic, so the same issue is with them. Generally used-up plastic products or components are contaminated by a variety of materials and accompanied by a lot of foreign matters, which are not eliminated completely by a conventional recycling process including separation and/or washing.
In the recycling process line of Film with Lens units, used-up products are separated according to the model and transported to respective disassembling lines where papers or labels covering the outside are removed and disassembled into respective components. Components are classified into two categories, i.e. reusing components and re-treating (recycling in narrow sense) ones. Reusing components are to be reused as components in the newly-manufactured products after being examined on the function, washed/cleaned and adjusted and re-treating components are to be used as re-treated raw materials for the newly-manufactured products.
The re-treating components from Film with Lens Unit are such ones as a front cover, a rear cover, a body portion where the film is loaded and a film winding knob, which are made of thermoplastic resin. Those retreating components are crushed into small pieces (chips) by a crusher.
The crushed plastics are washed by a shower of washing liquid to eliminate contamination and foreign matters. Japanese patents, No. 2604262, No. 2640786 and No. 2717020 show that mixture of crushed plastics and washing liquid are stirred in a washing tank, washing liquid uses surfactants and washing tank having tapered bottom is equipped with agitating blade. The crushed plastics are dried after washing, then are molten by heating. The molten plastic is fed to an extruder to form pellet of cylindrical shape (pelletizing). Those pellets are used-up by themselves or together with a virgin plastics for molding such components as a front cover, a rear cover, a body portion where the film is loaded and a film winding knob.
However, the pelletizing process demands a lot of heating energy and water consumption and yet quickens thermal degradation of plastics, specially that of the used-up plastic as it is heated to melt at least twice while once as for virgin plastic. The thermal degradation lowers physical properties such as mechanical strength and heating may produce some materials which gives ill effect to photographic quality.
As for washing, shower is not enough to remove the contamination and foreign matters. Thus a filter installed in the extruder is often blocked with the foreign matters. Operation of exchanging the filter is not easy because of high temperature, which lowers productivity. Available semi-automatic filter exchanger is very expensive. Aforementioned stirred tank washing apparatus with agitating blade can be available instead of shower-type washer. However, if clashed plastics is equal to or lighter than the washing liquid in specific gravity, which makes it difficult to wash every pieces of crushed plastics equally and to drain the crushed plastics and the washing liquid together after finishing washing because they are separated and the crushed plastics tend to float according to the respective specific gravity.
It is proposed that crushed plastic tips lighter than the washing liquid is washed in the washing tank while being in a netlike basket. However, it is troublesome and take a long time to put the plastics in the basket, handle the basket to set in the washing tank and take out them to evacuate the basket, which causes the washing apparatus to be complex and makes it difficult to automate the system.
Use of organic solvents or CFCs (chlorofluorocarbons) and other surfactants to increase washing power is not preferable these days in terms of operation environment in the site, running cost, liquid waste treatment cost and living environment.